If it were possible to clear the overbearing gauziness off every scene, The Conspirator wouldn't be half bad. This goofy cinematographic weather is supposed to alert you that you're watching a historical movie. It seems that during the early years of this American union, every shaft of light was saturated with dust motes. People could barely see each other. Obviously, a Civil War broke out.

Robert Redford directs, which means the movie has that familiar wholesomeness and is totally, predictably competent. It also means it's super-American. Like a dutiful inheritor of his own early cowboy-hippieism, this latter-day Redford is knitting up two moments: now (Guantánamo-times) and the panicky months immediately following the assassination of President Lincoln. There is a semihero in The Conspirator, but he ends up in metaphorical exile. It's not so much that the movie is trying to teach us a lesson so we won't repeat the mistakes of the past, it's more like remembering the first outbreak of an illness much later in its progression.

Mary Surratt, played by Robin Wright Penn (bony-faced), is the mother on trial for aiding and abetting the gang of Southern conspirators behind the antique bullet that took out Lincoln. This gang includes her son. She also has a daughter, but no husband. She is assigned a lawyer who fought in the Union Army (the great James McAvoy, underused).

Mary spends some of the movie suffering on a hay-covered prison floor, but it's the circus of her trial that's the most fun. She sits quietly (in the dustiest courtroom in the world), and a parade of juicy early-American stereotypes rolls by: rural rubes, drunken Irishmen, bright-eyed idealists, and the meanest possible bunch of burly militiamen-cum-judges—all manipulated by the puppet master of a floury-wigged Kevin Kline behind the scenes. It's a great real-life thriller story, filmed pretty well. Some good popcorn will tip the scales.